Selection by indication of potent antiretroviral therapy use in a large cohort of women infected with human immunodeficiency virus

To characterize selection factors related to therapy initiation, the author s investigated the extent to which key markers of human immunodeficiency vi rus (HIV) disease severity were associated with initiation of potent antire troviral therapy (ART). Logistic regression was used to determine the effec ts of CD4(+) cell count and HIV RNA level on potent ART initiation during 6 -month periods among 2,059 HIV-infected US women enrolled in the Women's In teragency HIV Study. Low CD4(+) counts and high HIV RNA levels were signifi cantly (p < 0.05) associated with initiation of potent ART. During all peri ods between April 1996 and March 1998, CD4(+) counts were more strongly ass ociated with potent ART initiation than HIV RNA levels were; however, durin g the last period, both were associated (odds ratio per 100 CD4(+)-count de crease = 1.17, p < 0.01; odds ratio per 1 log(10) increase in HIV RNA level = 1.48, p < 0.05), For a CD4(+) count of 500 cells/mt and an HIV RNA level of 5,000 copies/ml, the probability of potent ART initiation increased fro m 0.5% to16.8% between October 1995-March 1996 and October 1997-March 1998, suggesting earlier initiation of potent ART. Given the documented occurren ce of confounding by indication, prospectively collected, time-dependent da ta on markers of disease progression and therapy use should be considered w hen making population-level comparisons before and after introduction of po tent ART.